This invention relates to an apparatus for use in the improvement of oral health especially in dental hygiene and more particularly to a device which may be used by dentists, hygienists and other personnel in relation to the prevention and treatment of dental diseases.
Dental diseases include both dental caries (tooth decay) and a group of gum diseases, collectively referred to as xe2x80x9cperiodontal diseasesxe2x80x9d. The most common aetiological factor or causative agent in both tooth decay and gum diseases is the presence of dental plaque.
Historically, tooth decay was the most common of all human diseases effecting man throughout the world. Tooth decay is the result of demineralisation of firstly, the outer layer of tooth enamel and then, subsequently, by a similar demineralisation of the inner body of dentine within the tooth. This demineralisation is brought about by an acid attack on the tooth surface. This acid is most commonly derived from acidogenic activity of the microbiological flora within the plaque mass, as the flora metabolise the carbohydrate content of that same plaque mass, or other sugar compounds within the diet of the host.
However, since the introduction of fluoride into water supplies, toothpastes, drinks, foods, tablets, special solutions and gels applied by the dental professional and through other avenues, the fluoride content of human tooth enamel has increased to the point where many teeth are now much more resistant to acid attack and so dental caries (tooth decay) has declined in significance and incidence throughout the world.
Nevertheless, this relative xe2x80x9cstrengtheningxe2x80x9d of human tooth enamel has not addressed the main cause of dental caries, namely that of the presence of dental plaque. Thus, more recently there has been an increase in tooth decay on those tooth surfaces which are not covered by human tooth enamel, such as the roots of the tooth.
Moreover, the gums which comprise soft gingival tissue and the collection of periodontal fibres, connective tissue, cementum, periosteum and bone, commonly referred to as the xe2x80x9cperiodontal apparatusxe2x80x9d and which collectively support and retain the tooth in the mouth, also respond to the presence of dental plaque, to the point where this entire mechanism may break down and the tooth is lost.
Thus, periodontal or gum diseases themselves have now become amongst the most common of all diseases affecting humans throughout the world today and are now the major cause of adult tooth loss.
Ironically the most common cause of both tooth decay and gum diseases is dental plaque. The diagnosis, treatment and management of these two major dental diseases is within the exclusive domain and responsibility of the dental profession.
However, the control of the primary causative agent, dental plaque, is such an important and/or arduous task, that the profession has introduced a speciality and auxiliary discipline within the profession, called xe2x80x9cDental Hygienists and/or Therapistsxe2x80x9d. An important task of the dental clinician is to remove this damaging substance and to instruct the individual patient how best they can attain control of this menace.
However, the clinical challenge confronting the dentist, hygienist, therapist or other dental clinicians is exacerbated by the limitations of the tools available to them to perform these tasks.
Clearly, the incidence and resultant damage to human health caused by dental plaque would suggest that the profession is failing to address their responsibility in this area and, further, that the tools available to the professional and the patient are inadequate.
The present inventor has thoroughly researched the derivation, accumulation and application of dental plaque. As a direct result of this research, the inventor has designed a system that addresses the very basic requirements of plaque control and this information, technology and appliances form the basis of this patent application.
Dental Diseases
The two most common and significant of all dental diseases are:
1. Tooth decayxe2x80x94xe2x80x9cDental Cariesxe2x80x9d
2. Gum diseasesxe2x80x94xe2x80x9cPeriodontal Diseasesxe2x80x9d
Aetiology
The common primary causative agent to both these diseases is dental plaque.
Sites
1. Local
It is estimated that over 75% of dental diseases commence in between the teeth in the area referred to as the xe2x80x9cinter-proximalxe2x80x9d region and, more specifically and in the classic model, in an area extending from the point of contact between adjacent teeth to the gingival attachment level at the cemento-enamel junction, where the crown of the tooth meets the root of that tooth. This area may be referred to as the xe2x80x9cembrasure trianglexe2x80x9d.
This site is the most important of all dental disease sites, since it contains both hard (tooth) and soft (gum) tissues and so plaque retention in this area may give rise to both tooth decay and gum disease. This area may be referred to as the xe2x80x9chot spotxe2x80x9d of dental diseases.
The next most significant site for dental diseases, especially periodontal diseases is around the gum line on either the outer (xe2x80x9cfacialxe2x80x9d, xe2x80x9clabialxe2x80x9d or xe2x80x9cbuccalxe2x80x9d) or inner (xe2x80x9catralxe2x80x9d, xe2x80x9cpalatalxe2x80x9d or xe2x80x9clingualxe2x80x9d) surfaces of each tooth or in the gingival sulcus. This factor may be exacerbated by angled, rotated, tilted, crossed or crowded teeth, all of which facilitate the retention of dental plaque and make its removal more difficult.
The next most significant site in the prevention and treatment of dental caries are the deep fissures, which may occupy an area of the top, biting or xe2x80x9cocclusalxe2x80x9d surface of the tooth. In these areas, small particles of food and/or plaque may be pushed into these fissures and be difficult to remove with conventional devices. Depending upon the local anatomy, these fissures may also represent a very thin layer of tooth enamel and so be more vulnerable to acid attack.
Similar to the fissures, the next most significant site for dental caries to occur, may be in the anatomical anomalies referred to as xe2x80x9cpitsxe2x80x9d. These defects in the tooth enamel are often deep and may occur on either the outer (xe2x80x9cfacialxe2x80x9d, xe2x80x9clabialxe2x80x9d or xe2x80x9cbuccalxe2x80x9d) or inner (xe2x80x9clingualxe2x80x9d, xe2x80x9catrialxe2x80x9d or xe2x80x9cpalatalxe2x80x9d) surfaces of the tooth.
2. Regional
The above sites identify localised areas on or around the tooth and gum surfaces which are prone to most dental disease attack due to the accumulation and retention of dental plaque. It should be noted that dental plaque is generated daily within a normally healthy mouth. It is a sticky, viscous or gelatinous mass that may grow, unless removed effectively.
However, if dental plaque is let accumulate for more than one day, it may calcify to form calculus (sometimes called xe2x80x9ctartarxe2x80x9d). This is a harder, chalky mass which binds to the tooth surface and is much more difficult to remove than its softer precursor, dental plaque.
If left to grow and accumulate on the tooth surface, this calculus, being rough attracts more plaque around its mass and so the process continues, the calculus gets larger and more plaque accumulates around the tooth and/or gum surfaces.
A common source of the calcium necessary for this process to occur is the calcium ions, resident within saliva. Thus, at sites where the saliva enters the mouth and subsequent accumulation of calculus takes place, the risk of dental diseases commencing is increased. The most common sites so described are the inner surfaces of the lower anterior teeth (lingual surfaces of lower incisors) and the outer surfaces of the upper posterior teeth (buccal surfaces of upper molars). Any other site of surface roughness, which retains plaque, such as defective restorations or anatomical anomalies, also represents a disease risk site.
The present inventor has recognised that there exists a need for an effective device for the maintenance of oral hygiene and in particular, the maintenance of good periodontal hygiene.
Accordingly, the present invention consists in a dental prophylaxis handpiece comprising a shaft one end of which includes a connection means to accept a dental handpiece drive, the other end of the shaft including a pin with a longitudinal axis either parallel or at an angle to but not on the longitudinal axis of the shaft, one or more bearings disposed about the shaft so as to support the shaft in a casing which extends to encompass the shaft, the casing including a portion at one end to accept the dental handpiece drive and at the other end a housing into which the pin protrudes, the housing being adapted to retain a member comprising a mounting component and a head, which head is disposed outside of the housing and is for application to dental tissues, and to permit the pin to engage in a groove in the member in a manner such that operation of the dental handpiece drive causes the shaft to rotate which in turn imparts an oscillating arcuate motion to the member including the head.
In another aspect, the present invention further consists in an electrically driven handpiece comprising a shaft one end of which is adapted to drivingly connect to an electric motor, the other end of the shaft including a pin with a longitudinal axis either parallel or at an angle to but not on the longitudinal axis of the shaft, one or more bearings disposed about the shaft so as to support the shaft in a casing which extends to encompass the shaft, the casing including a portion at one end to contain the electric motor and a source of power for the motor and at the other end a housing into which the pin protrudes, the housing being adapted to retain a member comprising a mounting component and a head, which head is disposed outside of the housing and is for application to dental tissues, and to permit the pin to engage in a groove in the member in a manner such that operation of the electric motor causes the shaft to rotate which in turn imparts an oscillating arcuate motion to the member including the head.
Throughout this specification, unless the context requires otherwise, the word xe2x80x9ccomprisexe2x80x9d, or variations such as xe2x80x9ccomprisesxe2x80x9d or xe2x80x9ccomprisingxe2x80x9d, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
Oral Hygienexe2x80x94In Perspective
1. Inter-Proximal
The inter-proximal region and, in particular, the embrasure triangle, thus represents the most important site in the prophylaxis, or prevention of dental diseases.
However, the motion of conventional xe2x80x9cprophylaxis handpiecesxe2x80x9d and the shape of conventional xe2x80x9cprophylaxis headsxe2x80x9d are not capable of penetrating this confined and uniquely shaped area. Moreover, even if these devices are forced to penetrate this disease hot spot, their very continuous circular or rotary motion and poor head design may bring about a burning, burnishing and general danage to the local soft tissue, namely the gingival crest.
It should also be noted that the continuous circular or rotary motion of current devices imparts a centrifugal force which tends to propel plaque, blood, puss, bacteria, viruses, pathogens, saliva, oral debris and other matter in a perpendicular direction tangential to the working surface of the rotating head to cause a xe2x80x9csplatterxe2x80x9d and spread of infectious material and all other matter around the immediate working environment of the device and thereby expose disease transfer risks to all people within that environment.
Not surprisingly, then the profession is not able to address the very demands placed upon it by their responsibility to remove this menace and thereby prevent what is the most common disease process affecting human health throughout the world today.
Moreover, the continuous circular or rotary motion of current devices invites the device to engage in resistance of tissue surfaces which causes the device to xe2x80x9cskidxe2x80x9d off these surfaces and xe2x80x9crun offxe2x80x9d in an uncontrolled direction. Thus the operator must continuously xe2x80x9cfightxe2x80x9d this dangerous tendency- a factor which causes much frustration, fatigue and fury, let alone exposing the tissue to unnecessary damage.
Clearly, what is needed is a special, purpose built device which is not only capable of penetrating this disease hot spot, but which entertains such a motion that will effectively remove plaque but not cause damage to the tissue, is tissue friendly to both hard and soft tissues, promotes healing and which will actually massage any affected soft tissue back to a state of clinical health whilst not causing xe2x80x98splatterxe2x80x99 or spread of any pathogens or infectious matter.
The present inventor believes that the dental prophylaxis handpiece now provided meets this need.
2. Gum Line Surfaces
The next most essential ingredient in such an oral hygiene device is that it can effectively clean the gum line of all teeth, again, without causing damage to either the hard or soft tissues and that it should be capable of massaging any affected soft tissue back to clinical health.
The dental prophylaxis handpiece of the invention has been so designed to achieve both inter-proximal hygiene and gum surface debridement simultaneously, to not cause damage to either hard or soft tissue and to massage the soft tissue, all at the same time. This has been achieved by the selection of unique head designs and a sensitive arcuate motion delivered to that head by the unique mechanical design of the handpiece.
Moreover, xe2x80x9csplatterxe2x80x9d from conventional prophylaxis handpieces has caused so much concern amongst oral health care professionals, that some manufacturers have tried to develop xe2x80x9csplatter-freexe2x80x9d pastes and have designed special features within the rotating rubber cups to minimise this menacing effect and health care risk, resident within these devices.
In an attempt to combat the spread of infectious material caused by rotating devices, the oral health care profession has been forced to wear protective glasses, face masks, rubber gloves and other expressly protective utilities. This causes financial and enviromental burden which may be reduced through the use of the present invention.
3. Occlusal Surface Fissures
The occlusal surfaces, together with their deep fissures are difficult to clean with conventional rubber cups, bristle brushes and the common circular motion as is currently available through regular dental handpieces.
The present invention has been proven to be more efficient in terms of time and extent of debridement it performs in these often difficult to get to areas. Further, the preparation of the fissures for the preventive procedure referred to as xe2x80x9cfissure sealingxe2x80x9d is much more enhanced by the use of the present invention. Again, this feature is due to the exclusive design of the heads and the arcuate motion delivered to those heads by this handpiece.
4. Coronal Pits
Indeed most coronal abnormalities are difficult to clean, when using conventional prophylaxis handpieces. Especially, rubber cups are not capable of engaging these defects.
The unique head design and arcuate motion of the heads of the present invention has shown to be most effective in the debridement of these dental defects.
5. Intervention
The above features refer to prevention of the disease process. However, since dental diseases are often already under way in many patient""s mouths, the need for effective intervention is obvious. Unfortunately, the conventional prophylaxis handpieces are not capable of performing this important task, without considerable risk of further damage being imposed upon the very tissue we are trying to treat. This device performs this task as well.
The shaft of the handpiece may be circular or multi-sided in cross-sections. Preferably, the shaft is circular in cross-section.
In the event that a multi-sided shaft is chosen, it is important that such a shaft generally include one or more portions which are circular in section to allow for the disposition of one or more bearings to support the shaft in the casing. Alternatively, a ball bearing with a suitably shaped inner surface to correspond with the cross sectional shape of the shaft may be used.
Generally, irrespective of whether the shaft is circular or multi-sided in cross-section, two bearings will be used to support the shaft, a first bearing disposed about the shaft proximate the one end of the shaft and the second bearing about the shaft proximate the other end of the shaft.
For reasons of durability, it is desirable that the shaft is made of metal, although plastics materials may be used. The person skilled in the art would recognise that a variety of metals may be used including stainless steel, mild steel and other alloys.
Similarly, usually the one or more bearings will be made of metal. although plastics materials could be used. The material of construction and the design of the bearings need to be consistent with amongst other things, the rotational speed of the shaft. Examples of suitable bearings are journal bearings, roller bearings and ball bearings.
The connection means may comprise a slot in a face of the one end of the shaft. This slot may be multi-sided in cross-section.
Alternatively, the connection means may comprise a shank which projects out of a face of the one end of the shaft. This shank may be multi-sided in cross-section.
The nature of the connection means will be determined by the kind of dental handpiece drive used. To allow for maximum utility of the handpiece of the invention, the slot is arrayed to accept a drive from those drives that are used in the dental profession. These drives include handpiece drives such as Doriot. E-type, Borden and mid-west including that imparted by a piece intermediate between the dental motor drive and the disposable handpiece commonly referred to as a xe2x80x9cnose conexe2x80x9d. Note, however, that the shaft may be dimensioned or configured in any way to accept any drive.
Furthermore, the handpiece drive may rotate clockwise or anticlockwise at conventional speeds of 0-40,000 rpm. Gearing may be included so as to reduce the final rotation speed to 0-5,000 rpm from 0-40,000 rpm.
In the electrically driven handpiece aspect of the invention, the shaft is adapted to drivingly connect to an electric motor. This may occur by a variety of means including direct coupling to the shaft of the electric motor or through an appropriate combination of gears mounted on each shaft. The person skilled in the art will also recognise that a common shaft may used. In this embodiment, a single shaft projects out of the electric motor.
The other end of the shaft includes a pin having a longitudinal axis which is either parallel or at an angle to but not on the longitudinal axis of the shaft. Preferably the pin is mounted on a face of the other end of the shaft, Although dependent on the diameter of the shaft, preferably the pin will be about 1-3 mm from the centre of the shaft, most preferably about 2 mm. Preferably the pin will have a width of between about 1 and 2 mm, most preferably about 1.5 mm. Alternatively, the pin may be tapered with the widest dimension on the shaft.
A casing is used to contain the shaft and to provide a mounting for the bearing(s). The casing may be made from a variety of plastics materials and metals. In general terms, casings formed from metal, such as aluminium and its alloys, stainless steel and the like will be more durable and are capable of sterilisation by accepted means thereby allowing for reuse. Likewise, single use or disposable handpieces, when required, may be formed from less durable plastics material such as polypropylene, polycarbonates, or combinations thereof or any other plastic resin material.
To assist in assembly, the casing may be formed from two halves. In such an embodiment, the halves are preferably formed in longitudinally extending portions. The half portions will have suitable mating surfaces with means being provided to join the halves together. Such means may include one or more fasteners which pass through opening(s) in one half to mate with suitable receptacle(s) in the other half. For example, the fasteners may be screws with the receptacle(s) having corresponding portions to accept the screw thread.
Alternatively, the casing may be formed in one piece. For example, when made from synthetic plastics material, the casing may be injection or blow moulded.
In the electrically driven handpiece aspect, the casing also contains the electric motor and power source. For convenience, the power source may be one or more batteries, optionally rechargeable. Alternatively, the power source may comprise a suitable plug or socket for connection to a domestic power supply. In any event, preferably a switch will be mounted in or on the casing to allow for power to be supplied to the electic motor as required.
In one embodiment, the casing may be enlarged at the one end so as to more easily accept the dental handpiece drive. The portion of the casing between the enlarged section and the housing may be substantially cylindrical in shape, tapered or contra-angled. If tapered, the casing will taper inwardly from the enlarged section towards the housing. Note that the taper may be over a full or a part length of the casing. When part tapered, a substantially cylindrical portion of the casing will be adjacent the housing.
When the casing is contra-angled, generally a portion of the casing adjacent the enlarged section will be substantially cylindrical or tapered with the portion of the casing adjacent the housing contra-angled. In this context, xe2x80x9ccontra-angledxe2x80x9d refers to the acute angle formed between the longitudinal axis of the substantially cylindrical portion of the casing and the longitudinal axis of the contra-angled portion of the casing. Such a contra-angle is desirable as existing dental devices utilise this feature.
It follows that in embodiments that include a contra-angled casing, the shaft will comprise two shaft components. A first shaft component will include the connection means at one end and a first coupling means at the other end. The first shaft component will extend along the longitudinal axis of the substantially cylindrical portion. A second shaft component will include a second coupling means at one end and the pin at the other end. The second shaft component will extend along the longitudinal axis of the contra-angled portion.
Both the first and the second component shafts will be mounted in the casing on one or more bearings as appropriate in a manner such that the first and the second coupling means are in driving engagement. Similarly the shafts may engage any number of gears in order to reduce its final rotational speed from 0-40,000 rpm to 0-5.000 rpm or any speed in between 0-40,000 rpm.
Although the person skilled in the art will recognise that a variety of coupling means may be used, one preferred coupling means is the combination of a crown gear and a pinion gear. In this invention, the first coupling means and the second coupling means could be a combination of either gear.
It is also desirable that the casing be provided with a means on an outer surface thereof to enhance control and/or comfort of the handpiece. Such means may comprise flattened portions to form a casing having a polygonal cross-section or sunken grip points. Alternatively, raised portions may be provided on the outer surface of the casing for the same purpose.
The handpiece includes a housing into which the pin protrudes. This housing is adapted to retain a member which comprises a mounting component and a head. The head is disposed outside of the housing and is for application to dental tissue.
In protruding into the housing, the pin must be engageable with a groove in the mounting component such that operation of the dental handpiece drive causes the shaft to rotate which in turn imparts an oscillating arcuate motion to the member, including the head. The arcuate angle will usually be up to 90xc2x0, preferably up to about 45xc2x0.
Generally, the housing will be substantially cylindrical in shape. Preferably, the longitudinal axis of the housing is at an angle of between about 90xc2x0 and about 125xc2x0 with respect to the longitudinal access of the shaft. For ease of construction, the housing will usually be formed as an integral part of the casing.
The member, including the head, retained by the housing comprises a mounting component and a head. Preferably the mounting component is substantially cylindrical and is in sliding contact with an inner surface of the housing. Alternatively, the mounting component may have one or more bearing surfaces to engage an inner surface of the housing.
In a preferred embodiment, the pin engages in a groove which is disposed in the mounting component such that the groove extends in a plane through the longitudinal axis of the member. The groove may extend completely or partially along the member.
In another embodiment, the groove may extend in a plane through the transverse axis of the member. Again, the groove may extend completely or partially along the member.
In an embodiment wherein the mounting component is substantially cylindrical, preferably it is in frictional engagement with a surface of the housing so as to retain the member therein. This may be achieved by providing a rim formed on an upper surface of the mounting component, the rim bearing on an upper edge of the housing so as to retain the member in the housing.
Alternatively, the member may include a second groove in the mounting component, the groove extending transversely to engage a second pin disposed within the housing so as to retain the member therein.
Similarly any other means of retaining the member within the housing may be used, such as a latch or any other effective retention piece both in the member or the housing.
The present inventor has discovered that the width of the groove and the angles of its walls, together with the eccentricity of the pin directly affect the amplitude of the arc of the member, including the head particularly under light loading. By xe2x80x9ceccentricity of the pinxe2x80x9d it is meant the extent to which the pin is positioned away from the longitudinal axis of the shaft. However, when the head is loaded whilst in use in a narrow or tight space, this amplitude reduces considerably. This difference in amplitude of the arcuate oscillation is referred to in this specification as the xe2x80x9ctidal load slapxe2x80x9d this factor has proven to be an advantage, especially when dealing with the wide variations in the degree of dental crowding, gaps between teeth and the degree of massage necessary to effectively treat some gum conditions. This degree of tidal load slap also acts as a buffer to reduce any aggressive movement of the head and thereby minimise damage to the dental tissue.
Accordingly, it is preferred that the external width of the groove is about from 1 mm to 3 mm. Most preferably about 2 mm.
Similarly, the internal width of the groove is preferably about 0.5 mm to 2 mm, most preferably about 1 mm.
The depth of the groove is preferably about 1 mm to 3 mm, most preferably about 2 mm. In some embodiments, it may extend within the mounting component to be continuous with a hollow central portion formed therein.
The groove may have parallel sides or be flared internally or externally. In this context flaring internally refers to embodiments where the external width of a groove is less than the internal width of a groove. Similarly, flaring externally refers to embodiments where the external width of a groove is greater than the internal width of a groove.
Alternatively, the pin may be tapered and the groove angled to form a V-shape so that the internal surface of the groove engages the tapered surface of the pin at all times.
It will be appreciated that the mounting component and head may be integrally formed, formed separately and permanently joined or formed separately and separably joined. The advantage in providing a separably joinable head is that it allows for ready replacement.
As previously mentioned, the member comprises a mounting component and a head. The head is disposed outside of the housing and is for application to dental tissues.
Generally, a head will comprise an array of bristle brushes which are mounted on a base. The base may comprise or function as the mounting component.
The design of the bristle brushes will be such that the head is capable of penetrating the inter-proximal area and in particular the embrasure triangle as well as into deeper periodontal pockets and other dental tissues relevant to the formation of plaque or other dental disease activity.
Generally, the topographical trim of the heads may be pyramidal, conical, V-shaped, dished, domed triangular, square or a combination of these shapes. The angle of the topographical trim may vary from about 40xc2x0 to about 80xc2x0 with respect to the base of the head. This angle is critical to allow maximum penetration and activity within the range of naturally occurring inter-proximal areas.
In one preferred embodiment, the head comprises tufts of bristles mounted in the base and made from 600 series nylon. These provide ideal flexibility for general hygiene purposes, sufficient rigidity to remove dental plaque but are sufficiently resilient to provide a gentle massaging effect on the gums. This series of nylon are also more resistant to moisture contamination. Preferably, the length of bristles is between about 5 mm and about 15 mm with the average height of the highest bristles in the peak being about 10 mm.
In this embodiment, the number of bristles per tuft and the number of tufts per unit area of the base are important. In a preferred embodiment, there are 25 bristles per tuft but as required, this may vary from between 15 to 40 bristles per tuft. For this preferred embodiment, the tuft is about 1.5 mm diameter at the base. However, the diameter may vary from between about 1 to about 2 mm. In a particularly preferred embodiment, there is one tuft of bristles per 2 mm squared. However, this may vary from between one tuft per mm2 to one tuft per 4 mm2. This variation is necessary to cater for the wide variation in dental crowding arising from those people with wide gaps between the teeth to those which are crossed, crowded or tilted.
For guidance, the base of a single peaked head is about 7 mm2. However, this may vary from about 5 mm2 to 10 mm2.
In an alternative embodiment, the bristles may be arranged as a single tuft or mass rather than as one or more tufts.
Alternatively, the bristles may be made from any other nylon, plastics material, natural or synthetic material to provide filaments similar to those previously described as bristles.
In a further alternative embodiment, rather than in the form of bristles, the head may comprise a shape formed from a flexible or absorbent material such as rubber, silicone, synthetics plastics materials, felt, condensed paper, cork or wood. These heads may be used to apply medications to affected dental tissues either separately or simultaneously with the removal of dental plaque. Suitable shapes include conical and triangular pyrimidal.
As previously mentioned, various components of the handpiece of the invention may be made of metal, plastics materials or mixtures thereof. In general terms, those hand pieces made of plastics will be disposable, that is for single use. In one embodiment formed from plastics materials, the head may be non-removably incorporated in the hand piece. Alternatively, the head may be removable as previously described. Amongst the plastics materials that may be used are polypropylenes, polycarbonates and the like, mixtures thereof or any other suitable plastics materials.
In plastic handpieces of the invention the bearing(s) may exist as simple surface contact areas or any other form of bearing detail. Thus these bearings may be integral or separate from the shaft.
Those hand pieces formed from metal components will generally be reusable, that is they will be capable of cleaning and sterilisation.
For those embodiments formed from both plastics materials and metal components, it is possible to produce embodiments that are either reusable, disposable or both according to choice. However, in producing reusable composite hand pieces it is important to consider the nature of the plastics materials used to ensure that they are capable of being sterilised.